Occupant restraint system

ABSTRACT

An inflator of a vehicle occupant restraint system provided with a source of pressure fluid to inflate a cushion. A manifold receives the pressure fluid from the source and includes a nozzle through which the fluid accelerates to a supersonic flow. The nozzle has a throat that provides for the formation of a normal shock wave within the throat. A passage portion of the manifold is of generally uniform cross-sectional area and receives the supersonic fluid and the normal shock wave from the nozzle. A converging nozzle receives the fluid flow from the passage portion and has a throat for trapping the normal shock wave upstream therefrom to prevent the normal shock wave from traveling downstream of the passage portion and to decelerate the fluid flow to subsonic. A diffuser or apertured outlet portion receives the subsonic fluid from the converging nozzle and communicates the subsonic flow to an inflatable occupant restraint cushion.

United States Patent [191 Mason, Jr.

OCCUPANT RESTRAINT SYSTEM [75] Inventor: William T. Mason, Jr., Lake Orion,

Mich.

[73] Assignee: General Motors Corporation, Detroit, Mich.

[22] Filed: Nov. 13, 1972 [21] Appl. No.: 305,918

[52] US. Cl 280/150 AB, 73/147, 181/47 R, 222/3 [51] Int. Cl. 8601' 21/08 [58] Field of Search..... 280/150 AB; 73/147; 222/3; 181/47 R [56] References Cited UNITED STATES PATENTS 3,666,289 5/1972 Magyar 280/150 AB 2,696,110 12/1954 Eggers 73/147 2,911,787 11/1959 Barry 73/147 OTHER PUBLICATIONS Journal of Applied Physics, Hypersonic Research Facilities at the Ames Aeronautical Laboratory Vol. 21, Nov. 1950; p. 1150. Dynamics and Thermodynamics of Compressible Fluid Flow, One-Dimensional Supersonic Diffusers,

[451 Apr. 30, 1974 The Ronald Press Company, New York, 1958; pp. 143-147.

Primary Examinerl(enneth H. Betts Assistant Examiner-John P. Silverstrim Attorney, Agent, or Firm-Herbert Furman ABSTRACT An inflator of a vehicle occupant restraint system provided with a source of pressure fluid to inflate a cushion. A manifold receives the pressure fluid from the source and includes a nozzle through which the fluid accelerates to a supersonic flow. The nozzle has a throat that provides for the formation of a normal shock wave within the throat. A passage portion of the manifold is of generally uniform cross-sectional area and receives the supersonic fluid and the normal shock wave from the nozzle. A converging nozzle receives the fluid flow from the passage portion and has a throat for trapping the normal shock wave upstream therefrom to prevent the normal shock wave from traveling downstream of the passage portion and to decelerate the fluid flow to subsonic. A diffuser or apertured outlet portion receives the subsonic fluid from the converging nozzle and communicates the subsonic flow to an inflatable occupant restraint cushion.

3 Claims, 1 Drawing Figure A DIAPHRAGM ,0 NORMAL SHOCK CUSHION WAVE 20 ll 1 m a? x a CONVERGING- DIVERGING PASSAGE DIVERGING OUTLET NOZZLE PORTION I PORTION I PORTION FLUID PRESSURE SOURCE 125??? OCCUPANT RESTRAINT SYSTEM This invention relates to occupant restraint systems and, more particularly, to such systems having a manifold communicating the pressure fluid source and the inflatable cushion.

Vehicle occupant restraint systems have heretofore been provided which comprise a pressure fluid source that is communicated with an inflatable cushion by a manifold having an outlet end portion or diffuser provided with one or more rows of slots or flow outlet openings. In such systems, it has been found that a standing normal shock wave can exist in the vicinity of the flow outlet openings. The flow through the outlet openings upstream of the shock wave will be supersonic and the flow through the outlet openings downstream of the shock wave will be subsonic. The expansion of the fluid to ambient pressure as it flows through the upstream outlet openings occurs through a complex oblique shock wave system so that the flow losses through these openings will be more than the flow losses through the downstream outlet openings. The normal shock wave and the oblique shock wave system also contribute to the noise level of the system. There are, of course, additional losses associated with the flow from the source to the manifold.

In a preferred embodiment of the system, a manifold includes a converging-diverging nozzle that receives the pressure fluid from the source and through which the pressure fluid accelerates to a supersonic flow. The converging-diverging nozzle has a throat which provides for the formation of a normal shock wave within the throat. A passage portion of generally uniform cross-sectional area receives the supersonic flow and the normal shock wave from the converging-diverging nozzle. A converging nozzle receives the fluid flow from the passage portion and has a throat for trapping the normal sound wave upstream therefrom to prevent the normal shock wave from traveling downstream of the passage portion and to decelerate the fluid flow to a subsonic fluid flow. A diffuser or outlet portion of the manifold receives the subsonic fluid flow from the converging nozzle and communicates the subsonic fluid flow to the cushion.

The system of this invention reduces the flow losses and the noise level by controlling the location of the normal shock wave with respect to the flow outlet openings to the cushion. The shock wave is formed in a converging-diverging nozzle and is trapped upstream of the flow outlet openings of the manifold by a converging nozzle so that the flow through these openings is subsonic.

These and other objects of the present invention will become more fully apparent from the following detailed description and drawing which shows schematically an occupant restraint system embodying the present invention.

The occupant restraint system 10 includes a conventional cushion 12 positioned within the passenger compartment of a vehicle (not shown) for inflation and deployment when the system is conventionally actuated by a sensor (not shown).

The system 10 includes a conventional pressure fluid source 14, and a manifold 16 having a first convergingdiverging nozzle 18, a passage portion 20, a second converging nozzle 22, and a diffuser or an outlet portion 24 communicating with the cushion 12.

The source 14 is of any conventional type such as a gas generator or a pressure vessel or hybrid or augmented, which releases the pressure fluid to inflate an occupant restraint cushion 12 when actuated by a sensor (not shown). The source 14 is shown as a pressure vessel having a rupturable diaphragm 26 which is ruptured by detonators (not shown), to release pressure fluid to the nozzle 18 when the detonators are fired by the sensor. The fluid from source 14 is under sufficient pressure to attain supersonic fluid flow through the nozzle 18.

The nozzle 18 is shown as an outlet for the source 14. However, it should be understood that the nozzle 18 could alternatively be positioned within the source 14 or, could be located in some other position of greater disassociation than that shown in the drawing. The first nozzle 18 is of the converging-diverging, supersonic type and includes a converging portion 28, a throat 30, and a diverging portion 32. Although the diaphragm 26 is shown positioned within the throat 30 and between the converging and diverging portions 28 and 32, it should be understood that the diaphragm 26 could be otherwise positioned therein.

The passage portion 20 of the manifold 16 receives the fluid flow from the first nozzle 18 and has a generally uniform cross-sectional area greater than the crosssectional area of the throat 30. Further, although the passage portion 20 is shown as being of generally straight configuration, it should be understood that one or more bends or turns in the passage portion 20 would have no effect on the operation of the manifold if any such bends or turns were of the same uniform crosssectional area.

The second nozzle 22 of the manifold receives the fluid flow from the passage portion 20. Nozzle '22 has a converging portion 34 adjacent the downstream end of the passage portion 20, a throat 36 having a crosssectional area geater than the cross-sectional area of the throat 30 of the first nozzle 18 and less than the cross-sectional of the passage portion 20, and a diverging portion 38 which terminates in a downstream portion having a cross-sectional area equal to or greaterthan the cross-sectional area of the passage portion 20. i

The outlet portion 24 of the manifold 16 receives the fluid flow from the diverging portion 38 of the second nozzle 22. The outlet portion 24 has one or more rows of flow outlets or openings 40 which are spaced axially along the outlet portion 24 and which provide for the fluid flow to pass from the manifold 16 to the cushion 12 to inflate and deploy the cushion 12 within the passenger compartment of the vehicle. The outlet portion 24 has a generally uniform cross-sectional area equal to that of the downstream portion of the diverging portion 38 of the second nozzle 22 and, thus, is also equal to or greater than the cross-sectional area of the passage portion 20.

In operation, the diaphragm 26 within the throat 30 of the first nozzle 18 is ruptured when the detonators (not shown) of the system 10 are tired by the sensor. The pressure fluid source 14 releases pressure fluid to the first nozzle 18. The pressure fluid accelerates to a sonic fluid flow as it flows through the converging portion 28 of the first nozzle 18. The throat 30 of the first nozzle 18 causes the formation of a normal shock wave within the throat which travels downstream therefrom with the fluid flow. The diverging portion 32 of the first nozzle 18 provides for expansion of the fluid flow which causes the sonic fluid flow to accelerate to super sonic fluid flow. The fluid flow and the normal shock wave travel downstream within the passage portion to the second nozzle 22 where the fluid flow is contracted by the converging portion 34 and throat 36. The converging portion 34 and throat 36 of the second nozzle 22 serve to trap the normal shock wave upstream therefrom and within the downstream end of the passage portion 20. Thus, the second nozzle 22 prevents the normal shock wave from traveling further downstream into the outlet portion 24 of the manifold. Further, this results in the supersonic fluid flow being decelerated to subsonic fluid flow. The subsonic fluid flow passes from the diverging portion 38 of the second nozzle 22 into the outlet portion 24 and exits from the manifold through the openings 40 in order to inflate and deploy the cushion 12.

The foregoing disclosure relates to only one embodiment of the present invention which may be modified within the scope of the appended claims.

What is claimed is:

1. In a vehicle occupant restraint system having a source of pressure fluid and an inflatable cushion, a manifold communicating the source and cushion and comprising: nozzle means receiving pressure fluid from the source for accelerating the pressure fluid to supersonic fluid flow, said nozzle means having a throat providing for the formation of a normal shock wave within said throat; a passage portion of generally uniform cross-sectional area for receiving the supersonic fluid flow and normal shock wave from said nozzle; a converging nozzle receiving the fluid flow from said passage portion and having a throat for trapping the normalshock wave upstream therefrom to prevent the normal shock wave from traveling downstream of said passage portion and to decelerate the fluid flow to a subsonic fluid flow; and an outlet portion receiving the subsonic fluid flow from said converging nozzle and communicating the subsonic fluid flow to the cushion.

2. In a vehicle occupant restraint system having a source of pressure fluid and an inflatable cushion, a manifold communicating the source and cushion and comprising: a converging-diverging nozzle receiving the pressure fluid from the source for accelerating the pressure fluid to a supersonic flow, said convergingdiverging nozzle having a throat providing for the formation of a normal shock wave within said throat; a passage portion having a generally uniform crosssectional area greater than the cross-sectional area of said throat of said converging-diverging nozzle receiving the supersonic fluid flow and the normal shock wave from said converging-diverging nozzle; a converging nozzle receiving the fluid flow from said passage portion and having a throat with a cross-sectional area greater than the cross-sectional area of said throat of said converging-diverging nozzle for trapping the normal shock wave upstream therefrom to prevent the normal shock wave from traveling downstream of said passage portion and to decelerate the fluid flow to a subsonic fluid flow; and an outlet portion having a generally uniform cross-sectional area equal to or greater than the cross-sectional area of said passage portion and receiving the subsonic fluid flow from said converging nozzle amd communicating the subsonic flow to the cushion.

3. in a vehicle occupant restraint system having a source of pressure fluid and an inflatable cushion, a manifold communicating the source and the cushion and comprising: a first nozzle associated with said source of fluid pressure to receive the pressurized fluid therefrom, said first nozzle having a converging portion through which the pressurized fluid accelerates to a sonic fluid flow, said firstnozzle having a throat to provide for the formation of a normal shock wave within said throat, said first nozzle having a diverging portion for expanding the fluid flow and through which said sonic fluid flow accelerates to a supersonic fluid flow; a passage portion having a generally uniform crosssectional area greater than the cross-sectional area of said throat of said first nozzle and adapted to receive the supersonic fluid flow and normal shock wave; a second nozzle having a converging portion terminating in a throat having a cross-sectional area greater than the cross-sectional area of said throat of said first nozzle and less than the cross-sectional area of said passage portion, said second nozzle receiving the fluid flow from said passage portion and contracting the fluid flow to trap the normal shock wave in the downstream end of said passage portion to prevent the normal shock wave from traveling downstream of said passage portion and to decelerate the fluid flow to a subsonic fluid flow, said second nozzle having a diverging portion receiving and passing the subsonic fluid flow; and an outlet portion having a generally uniform crosssectional area equal to or greater than the crosssectional area of said passage portion and receiving the subsonic fluid flow from said second nozzle, said outlet portion having a plurality of exit openings for communicating the subsonic fluid flow to the cushion. 

1. In a vehicle occupant restraint system having a source of pressure fluid and an inflatable cushion, a manifold communicating the source and cushion and comprising: nozzle means receiving pressure fluid from the source for accelerating the pressure fluid to supersonic fluid flow, said nozzle means having a throat providing for the formation of a normal shock wave within said throat; a passage portion of generally uniform crosssectional area for receiving the supersonic fluid flow and normal shock wave from said nozzle; a converging nozzle receiving the fluid flow from said passage portion and having a throat for trapping the normal shock wave upstream therefrom to prevent the normal shock wave from traveling downstream of said passage portion and to decelerate the fluid flow to a subsonic fluid flow; and an outlet portion receiving the subsonic fluid flow from said converging nozzle and communicating the subsonic fluid flow to the cushion.
 2. In a vehicle occupant restraint system having a source of pressure fluid and an inflatable cushion, a manifold communicating the source and cushion and comprising: a converging-diverging nozzle receiving the pressure fluid from the source for accelerating the pressure fluid to a supersonic flow, said converging-diverging nozzle having a throat providing for the formation of a normal shock wave within said throat; a passage portion having a generally uniform cross-sectional area greater than the cross-sectional area of said throat of said converging-diverging nozzle receiving the supersonic fluid flow and the normal shock wave from said converging-diverging nozzle; a converging nozzle receiving the fluid flow from said passage portion and having a throat with a cross-sectional area greater than the cross-sectional area of said throat of said converging-diverging nozzle for trapping the normal shock wave upstream therefrom to prevent the normal shock wave from traveling downstream of said passage portion and to decelerate the fluid flow to a subsonic fluid flow; and an outlet portion having a generally uniform cross-sectional area equal to or greater than the cross-sectional area of said passage portion and receiving the subsonic fluid flow from said converging nozzle amd communicating the subsonic flow to the cushion.
 3. In a vehicle occupant restraint system having a source of pressure fluId and an inflatable cushion, a manifold communicating the source and the cushion and comprising: a first nozzle associated with said source of fluid pressure to receive the pressurized fluid therefrom, said first nozzle having a converging portion through which the pressurized fluid accelerates to a sonic fluid flow, said first nozzle having a throat to provide for the formation of a normal shock wave within said throat, said first nozzle having a diverging portion for expanding the fluid flow and through which said sonic fluid flow accelerates to a supersonic fluid flow; a passage portion having a generally uniform cross-sectional area greater than the cross-sectional area of said throat of said first nozzle and adapted to receive the supersonic fluid flow and normal shock wave; a second nozzle having a converging portion terminating in a throat having a cross-sectional area greater than the cross-sectional area of said throat of said first nozzle and less than the cross-sectional area of said passage portion, said second nozzle receiving the fluid flow from said passage portion and contracting the fluid flow to trap the normal shock wave in the downstream end of said passage portion to prevent the normal shock wave from traveling downstream of said passage portion and to decelerate the fluid flow to a subsonic fluid flow, said second nozzle having a diverging portion receiving and passing the subsonic fluid flow; and an outlet portion having a generally uniform cross-sectional area equal to or greater than the cross-sectional area of said passage portion and receiving the subsonic fluid flow from said second nozzle, said outlet portion having a plurality of exit openings for communicating the subsonic fluid flow to the cushion. 